This invention relates to internal combustion engine spark distributor caps and particularly to distributor caps having a sealing or leakproof means to inhibit moisture formation within the cap interior surface, thereby preventing failure of the cap during high-humidity engine operation. The invention also relates to detecting means to indicate the humidity of the air within the distributor cap.
There has been a long existent and bothersome problem of difficult engine starting during rainy spells or under high-humidity operating conditions, which problem has been found to center in the ignition distributor. This problem has been aggrevated in certain vehicle installations due to the fact that the distributor location in the vehicle engine compartment may have very little road water splash protection and/or air inlet apertures or ducting for the engine compartment tend to pass large volumes of moisture-saturated air around the distributor unit such that moisture is deposited on the exterior of and introduced to the interior of the distributor cap.
It has been determined that a major problem associated with high-humidity distributor operating conditions is conductivity of the cap interior surface. Such conductivity is promoted both by the inherent low electrical resistance of an aqueous film present on the cap interior surface and by the deterioration of that surface, resulting in an uneven sparking operation and ultimate failure of desired spark action.
Distributor cap conductivity resulting from deterioration of the cap interior surface is especially promoted by the presence of moisture-laden air within the cap during operating periods. At such times, undesirable electrical shorting that can occur (i.e., in moist atmosphere) between closely positioned high-tension contact studs stimulates the formation of a conductive film or path.